Stiffness measuring mechanism, rotary timber charger with stiffness measuring mechanism and method of operation for same

ABSTRACT

A rotary timber charger having a charging assembly with at least two spaced apart transfer wheels each having at least one timber piece grasping assembly operative to grasp a section of a piece of timber at a grasping position, release the section of the piece of timber at a release position, and retain the section of the piece of timber therebetween. The rotary timber charger also comprises a stiffness measuring mechanism with at least one load application wheel positioned between consecutive transfer wheels and each comprising at least one load application member configured to momentarily apply a load on the piece of timber and at least one surface position measuring assembly measuring a first position and a second position of a measure surface, angularly spaced-apart from one another, with the load being applied in at least one of the first position and the second position of the measure surface.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) of U.S.provisional patent application No. 62/065,875 which was filed on Oct.20, 2014. The entirety of the aforementioned application is hereinincorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of timber stiffnessmeasurement and timber grading. More particularly, it relates to amechanism for measuring the stiffness of a piece of timber, a rotarytimber charger including a mechanism for measuring the stiffness of apiece of timber and a method of operation for same.

BACKGROUND

It is known in the art to measure the stiffness of timber pieces inorder to perform non-destructive stress grading thereof based on themeasured stiffness and correlated strength of each one of the timberpieces.

Known methods to measure the stiffness of timber pieces commonly includetaking a number of measurements of stiffness over a length of a piece oftimber (for example, on its side in the case of a plank). In order toperform such measurements, each one of the pieces of timber can be movedeither longitudinally or transversally, with supports for supporting asection of the piece of timber in place and a load to apply a force onanother section of the piece of timber, between the supports.

Canadian patent application no. 2,363,092 discloses an apparatus forgrading timber pieces, where measuring of the stiffness of each piece oftimber is performed by applying a force to the piece of timber, at apoint intermediate its length, as the piece of timber is supported at ornear the ends thereof, without moving the piece of timber lengthwise. Inorder to measure the stiffness of the piece of timber, the patentapplication describes that either a predetermined force can be appliedby a ram and the resulting deflection of the piece of timber measured,or the force required to deflect the piece of timber by a predeterminedamount can be measured. The document discloses that a single measurementcan be taken by, for example, applying a force and measuring theresulting deflection of the piece of timber, or two or more measurementscan be taken by applying a first predetermined force and measuring theresulting deflection and subsequently applying, for example, a secondhigher force and measuring the resulting deflection.

The above described methods and apparatuses to grade pieces of timberusing measurement of a stiffness thereof however suffer from severaldrawbacks. Indeed, in order to measure the stiffness of the timberpieces using such methods and apparatuses, a dedicated machine must beadded to the production line, which requires additional space andincreases the time required for a piece of timber to travel along theproduction line. Moreover, given that pieces of timber are not allidentical, the measurements obtained for a piece of timber can be biasedby the natural curvature of the piece of timber and/or by imperfections(tears, holes, slits or the like) on the surface from which themeasurements are taken.

In view of the above, there is a need for an improved mechanism formeasuring the stiffness of a piece of timber which would be able toovercome or at least minimize some of the above-discussed prior artconcerns.

BRIEF SUMMARY OF THE INVENTION

According to a first general aspect, there is provided a rotary timbercharger. The rotary timber charger comprises a charging assembly with atleast two transfer wheels spaced apart from one another and mounted to amain rotatable shaft, each one of the at least two transfer wheelshaving at least one timber piece grasping assembly operative to grasp asection of a piece of timber at a grasping position, release the sectionof the piece of timber at a release position, and retain the section ofthe piece of timber between the grasping position and the releaseposition. The rotary timber charger also comprises a stiffness measuringmechanism with at least one load application wheel positioned betweenconsecutive transfer wheels, each one of the at least one loadapplication wheel comprising at least one load application memberconfigured to momentarily apply a load on the piece of timber retainedby a corresponding one of the at least one timber piece graspingassembly of the consecutive ones of the at least two transfer wheels.The stiffness measuring mechanism also comprises a deformation measuringsystem with at least one surface position measuring assembly measuring afirst position of a measure surface of the piece of timber and a secondposition of the measure surface of the piece of timber, the secondposition of the measure surface being angularly spaced-apart from thefirst position, with the load being applied by the at least one loadapplication member of the at least one load application wheel in atleast one of the first position and the second position of the measuresurface.

In an embodiment, the main rotatable shaft of the charging assemblyrotates continuously.

In an embodiment, the first position of the measure surface is anangular position thereof without the load being applied by the loadapplication member of the at least one load application wheel.

In an embodiment, the at least one load application wheel is mounted tothe main rotatable shaft and rotates simultaneously with the at leasttwo transfer wheels.

In an embodiment, each one of the at least one load application memberof the at least one load application wheel includes a load applicationrod mounted to the load application wheel and a translation actuatoroperatively connected thereto to translate the load application rodbetween an inactive configuration wherein a timber piece abutting end ofthe load application rod is spaced apart from a contact surface of thepiece of timber, opposed to the measured surface, and an activeconfiguration wherein the timber piece abutting end of the loadapplication rod abuts the contact surface of the piece of timber.

In an embodiment, the at least one load application wheel comprises aplurality of load application members and each one of the at least twotransfer wheels comprises a plurality of grasping assemblies, the amountof load application members corresponding to the amount of graspingassemblies and each one of the plurality of load application membersbeing angularly aligned with a corresponding one of the plurality ofgrasping assemblies.

In an embodiment, the rotary timber charger further comprises a rotaryencoder indicating an angular position of the main rotatable shaft andthe at least one surface position measuring assembly of the deformationmeasuring system is calibrated using the rotary encoder.

In an embodiment, the at least one surface position measuring assemblyof the deformation measuring system includes a first surface positionmeasuring assembly configured to measure one of the position of themeasure surface of the piece of timber without the load being applied bythe load application member of the at least one load application wheeland the position of the measure surface of the piece of timber with theload being applied by the load application member of the at least oneload application wheel and a second surface position measuring assemblyconfigured to measure the other one of the position of the measuresurface of the piece of timber without the load being applied by the atleast one load application member of the load application wheel and theposition of the measure surface of the piece of timber with the loadbeing applied by the load application member of the at least one loadapplication wheel.

In an embodiment, each one of the at least one timber piece graspingassembly comprises a first and a second grasping members cooperating toengage opposite surfaces of the piece of timber and the load applicationmember is mounted peripherally to a respective one of the at least oneload application wheel and extends substantially tangentially thereto.

According to another general aspect, there is also provided, a stiffnessmeasuring mechanism for a rotary timber charger having a rotatablecharging assembly including at least one set of timber piece graspingassemblies and being operative to transfer successive pieces of timberfrom a first carrier assembly to a second carrier assembly. Thestiffness measuring mechanism comprises at least one load applicationwheel positioned between consecutive grasping assemblies of the at leastone set of timber grasping assemblies of the rotatable chargingassembly, the at least one load application wheel comprising at leastone load application member configurable between an inactiveconfiguration where no load is applied on a transferred piece of timberand an active configuration where a load is applied on the transferredpiece of timber. The stiffness measuring mechanism also comprises adeformation measuring system comprising at least one surface positionmeasuring assembly measuring a first position of a measure surface ofthe transferred piece of timber and a second position of the measuresurface of the transferred piece of timber. The the stiffness measuringmechanism operates concurrently with the rotatable charging assemblytransferring the successive pieces of timber from the first carrierassembly to the second carrier assembly.

In an embodiment, the first position of the measure surface of thetransferred piece of timber corresponds to the inactive configuration ofa corresponding one of the at least one load application member and thesecond position of the measure surface of the transferred piece oftimber corresponds to the active configuration of the corresponding oneof the at least one load application member.

In an embodiment, the charging assembly of the rotary timber chargercomprises a main shaft rotatable to engage in rotation the at least oneset of timber piece grasping assemblies and the at least one loadapplication wheel.

In an embodiment, the stiffness measuring mechanism further comprises arotary encoder indicating an angular position of the main rotatableshaft and the at least one surface position measuring assembly of thedeformation measuring system is calibrated using the rotary encoder.

In an embodiment, each one of the at least one load application memberof the at least one load application wheel includes a load applicationrod mounted to the load application wheel and a translation actuatoroperatively connected thereto to translate the load application rodbetween the inactive configuration wherein a timber piece abutting endof the load application rod is spaced apart from a contact surface ofthe piece of timber, opposed to the measured surface, and the activeconfiguration wherein the timber piece abutting end of the loadapplication rod abuts the contact surface of the piece of timber.

In an embodiment, the at least one load application wheel comprises aplurality of load application members and the rotatable chargingassembly comprises at least two transfer wheels, wherein each one of theat least two transfer wheels comprises a plurality of graspingassemblies, the amount of load application members corresponding to theamount of grasping assemblies and each one of the plurality of loadapplication members being angularly aligned with a corresponding one ofthe plurality of grasping assemblies.

According to another general aspect, there is also provided a method formeasuring a stiffness of successive pieces of timber, for each one ofthe successive pieces of timber. The method comprises the steps of:grasping the piece of timber at a grasping position; rotating the pieceof timber towards a release position; and releasing the piece of timber.Concurrently with the step of rotating the piece of timber towards therelease position, the method further comprises measuring a position of ameasure surface of the piece of timber at a first measurement position;applying a load on the piece of timber; measuring a position of themeasure surface of the piece of timber at a second measurement positionas the load is applied on the piece of timber; and removing the loadfrom the piece of timber.

In an embodiment, the step of rotating the piece of timber towards therelease position is performed by a continuous rotation of the piece oftimber.

In an embodiment, the first measurement position is the position of themeasure surface of the piece of timber without the load being applied onthe piece of timber.

In an embodiment, the step of grasping the piece of timber at a graspingposition and continuously rotating the piece of timber towards a releaseposition comprise temporarily engaging opposite surfaces of the piece oftimber at grasping positions along a length of the piece of timber.

In an embodiment, the step of applying a load on the piece of timbercomprises engaging the piece of timber using at least one loadapplication member, along at least one section of the piece of timberlocated between the grasping positions.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages and features will become more apparent uponreading the following non-restrictive description of embodimentsthereof, given for the purpose of exemplification only, with referenceto the accompanying drawings in which:

FIG. 1 is a top perspective view of a rotary timber charger with astiffness measuring mechanism, according to an embodiment.

FIG. 2 is a front elevation view, enlarged, of a rotatable chargingassembly of the rotary timber charger including the stiffness measuringmechanism of FIG. 1.

FIG. 3 is a side elevation view, enlarged, of a load application wheelof the rotary timber charger including the stiffness measuring mechanismof FIG. 1, shown with a cover partially removed.

FIG. 4a is a cross-sectional side view of the rotary timber chargerincluding the stiffness measuring mechanism of FIG. 1, showing a pieceof timber being grasped by the rotatable charging assembly.

FIG. 4b is a cross-sectional side view of the rotary timber chargerincluding the stiffness measuring mechanism of FIG. 1, showing aninitial measurement of a position of a measure surface of the piece oftimber grasped by the rotatable charging assembly.

FIGS. 4c and 4d are respectively a perspective view, enlarged, and across-sectional side view of the rotary timber charger including thestiffness measuring mechanism of FIG. 1, showing a force being appliedon the piece of timber by a load application rod of the load applicationwheel and a simultaneous measurement of a position of the measuresurface of the piece of timber.

FIG. 4e is a cross-sectional side view of the rotary timber chargerincluding the stiffness measuring mechanism of FIG. 1, with the loadapplication rod disengaged from the piece of timber.

FIG. 4f is a cross-sectional side view of the rotary timber chargerincluding the stiffness measuring mechanism of FIG. 1, showing a pieceof timber being released from the rotatable charging assembly.

DETAILED DESCRIPTION

In the following description, the same numerical references refer tosimilar elements. The embodiments, geometrical configurations, materialsmentioned and/or dimensions shown in the figures or described in thepresent description are embodiments only, given solely forexemplification purposes.

Moreover, although the embodiments of a stiffness measuring mechanismand rotary timber charger including the stiffness measuring mechanismand corresponding parts thereof consist of certain geometricalconfigurations as explained and illustrated herein, not all of thesecomponents and geometries are essential and thus should not be taken intheir restrictive sense. It is to be understood, as also apparent to aperson skilled in the art, that other suitable components andcooperation thereinbetween, as well as other suitable geometricalconfigurations, can be used for the stiffness measuring mechanism androtary timber charger including the stiffness measuring mechanism, aswill be briefly explained herein and as can be easily inferred herefromby a person skilled in the art. Moreover, it will be appreciated thatpositional descriptions such as “above”, “below”, “left”, “right” andthe like should, unless otherwise indicated, be taken in the context ofthe figures and should not be considered limiting.

Referring generally to FIG. 1, in accordance with one embodiment, thereis provided a rotary timber charger 10. The rotary timber charger 10includes a first carrier assembly 12 operative to convey successivepieces of timber 11 (only one piece of timber 11 is shown in FIG. 1),such as without being limitative, wood planks, boards or the like,towards a rotatable charging assembly 20 and a second carrier assembly14 operative to subsequently convey the pieces of timber 11 away fromthe rotatable charging assembly 20. Thus, the rotatable chargingassembly 20 is mounted between the first carrier assembly 12 and thesecond carrier assembly 14. In the embodiment shown, the first carrierassembly 12 and the second carrier assembly 14 include a plurality ofspaced apart and substantially parallel conveyor chains 12 a, 14 a toconvey the pieces of timber 11 transversally. One skilled in the artwould however understand that, in alternative embodiments, the firstcarrier assembly 12 and/or the second carrier assembly 14 can beembodied by any other conveyor arrangement which allow the pieces oftimber 11 to be conveyed transversally to and from the rotatablecharging assembly 20.

In view of the above, one skilled in the art will understand that therotary timber charger 10 can be part of a production line (not shown)which extends along a longitudinal axis X thereof, substantiallyperpendicular to the length of the pieces of timber 1, with the piecesof timber 11 being transversally conveyed along the longitudinal axis Xof the production line. Hence, it will be understood that the pieces oftimber 11 are conveyed along the longitudinal axis X of the productionline as they are conveyed along the first and second carrier assemblies12, 14 and the rotatable charging assembly 20 of the rotary timbercharger 10.

As mentioned above, the rotatable charging assembly 20 transfers thepieces of timber 11 from the first carrier assembly 12 to the secondcarrier assembly 14. In order to perform such transfer, as shown in FIG.2, the rotatable charging assembly 20 includes at least two transferwheels 24 spaced apart from one another and mounted to a main rotatableshaft 21. In an embodiment, the main rotatable shaft 21 continuouslyrotates about its rotation axis. Referring now to FIG. 4a , there isshown that each one of the transfer wheels 24 includes at least onetimber piece grasping assembly 22 operative to grasp a section of atransferred piece of timber 11, at a grasping position, temporarilyretain the section of the transferred piece of timber 11 during arotation of the transfer wheel 24 towards a release position (the pieceof timber 11 consequently also being rotated), and subsequently releasethe transferred piece of timber 11 at the release position. In theembodiment shown, each timber piece grasping assembly 22 includes afirst grasping member 22 a and a second grasping member 22 b whichcooperate to temporarily engage opposite surfaces of the transferredpiece of timber 11 to perform the grasping, temporary retention andsubsequent release of the section of the piece of timber 11 required fortransfer thereof. In an embodiment, the first grasping member 22 a andsecond grasping member 22 b continuously retain the pieces of timberduring the temporary retention.

In an embodiment, the transfer wheels 24 carry the transferred piece oftimber 11 between the grasping position and the release position alongat least 90° and less than about 270° and, in a particular embodiment,less than about 180°.

One skilled in the art will understand that each one of the at least twotransfer wheels 24 has the same amount of grasping assemblies 22, suchas to define sets of corresponding grasping assemblies 22 angularlyaligned with one another along the at least two transfer wheels 24.Hence, in operation, each set of corresponding grasping assemblies 22 ofthe at least two transfer wheels 24, grasp, maintain and release thetransferred pieces of timber 11 simultaneously.

In the embodiment shown, each one of the transfer wheels 24 includes aplurality of angularly spaced-apart timber piece grasping assembly 22,each one including a first grasping member 22 a and a second graspingmember 22 b.

In the embodiment shown, two transfer wheels 24 are provided. Each oneof the transfer wheels 24 is positioned for an associated timber piecegrasping assembly 22 to grasp a section of the transferred piece oftimber 11 close to an end thereof, during the transfer from the graspingposition (on the first carrier assembly 12) to the release position (onthe second carrier assembly 14). One skilled in the art will understandthat, in an alternative embodiment, more than two transfer wheels 24 canbe provided along a width of the rotatable charging assembly 20, suchthat grasping assemblies 22 of terminal transfer wheels 24 (i.e.transfer wheels 24 positioned at the ends of the rotatable chargingassembly 20) can grasp a section of the transferred pieces of timber 11proximate to an end thereof and grasping assemblies 22 of intermediatetransfer wheels 24 (i.e. transfer wheels 24 other than the terminaltransfer wheels 24) engage a section of the transferred pieces of timber11 between the terminal transfer wheels 24.

In order to measure a stiffness of each one of the pieces of timber 11being transferred by the rotatable charging assembly 20, the rotatablecharging assembly 20 also includes a stiffness measuring mechanism 30.

Referring now to FIGS. 2 and 3, there is shown that, in the embodimentshown, the stiffness measuring mechanism 30 includes at least one loadapplication wheel 32, with at least one load application member 33,operative to apply a momentary load (or force) on a transferred piece oftimber 11, as it is being transferred by the rotatable charging assembly20 from the first carrier assembly 12 to the second carrier assembly 14.For example and without being limitative, in an embodiment, themomentary load can be applied during a range of between about 50milliseconds and about 150 milliseconds. Referring to FIG. 4a , there isshown that the stiffness measuring mechanism 30 also includes adeformation measuring system 38 operative to determine the deformationof the transferred piece of timber 11 upon application of the loadthereon, based on measures of the transferred piece of timber 11. Eachload application wheel 32 is mounted to the main rotatable shaft 21,between consecutive ones of the transfer wheels 24. Therefore, it willbe understood that, in an embodiment (not shown) where more than twotransfer wheels 24 are mounted to the main rotatable shaft 21, multipleload application wheels 32 can be mounted to the main rotatable shaft21, each one of the multiple load application wheel 32 being positionedbetween consecutive ones of the transfer wheels 24.

In the embodiment shown, a single load application wheel 32 is mountedto the main rotatable shaft 21 and is centered between the correspondingtransfer wheels 24. One skilled in the art will understand that, in analternative embodiment, the load application wheel 32 could beoff-center relative to the adjacent ones of the transfer wheels 24.Moreover, one skilled in the art will understand that, in anotheralternative embodiment, more than one load application wheel 32 can bemounted to the main rotatable shaft 21, between adjacent ones of thetransfer wheels 24.

Referring to FIG. 3, in the embodiment shown, each load applicationmember 33 includes a load application rod 34 peripherally mounted to theload application wheel 32 and extending substantially tangentiallythereto. Each load application member 33 also includes a translationactuator 35 operatively connected to a respective one of the loadapplication rod 34. Each translation actuator 35 is operative tomomentarily drive the load application rod 34 longitudinally, to movethe load application rod 34 towards the transferred piece of timber 11.More particularly, the translation actuator 35 is operative tomomentarily drive the load application rod 34 in a manner such that atimber piece abutting end thereof extends outward of a peripheral edgeof the load application wheel 32. The outward movement of the loadapplication rod 34 results in the load application rod 34 contacting acontact surface 11 a of the timber element 11, thereby applying a forceon the transferred piece of timber 11 during a momentary time period.The translation actuator 35 also operates to subsequently retract theload application rod 34 to remove the force applied on the contactsurface 11 a of the transferred piece of timber 11. Thus, the loadapplication rod 34 translates between an inactive configuration whereinit is spaced apart from the contact surface 11 a of the transferredpiece of timber 11 and an active configuration wherein its timber pieceabutting end abuts the contact surface 11 a of the transferred piece oftimber 11 maintained by the timber piece grasping assembly 22 of thetransfer wheels 24. In an embodiment, in the inactive configuration, theload application rod 34, including the timber piece abutting end, isentirely located inside the periphery (i.e. inside the peripheral edge)of the load application wheel 32.

In an embodiment, the amount of load application rods 34 of each loadapplication wheel 32 is similar to the amount of sets of graspingassemblies 22 of the transfer wheels 24, such that each one of the loadapplication rods 34 is associated with one of the sets of graspingassemblies 22 of the transfer wheels 24. As will be easily understood byone skilled in the art, given that, in the embodiment shown, each loadapplication wheel 32 and transfer wheels 24 are mounted to a common mainrotatable shaft 21, the load application wheel 32 and transfer wheels 24rotate at a similar frequency of rotation (rpm) and remain in the sameangular position relative to one another throughout operation of therotary timber charger 10.

In an embodiment, the rotatable charging assembly 20 includes anelectronic control system operatively connected to the graspingassemblies 22 of the transfer wheels 24 and the translation actuators 35operatively connected to the load application rods 34 such that theoperation of each set of grasping assemblies 22 for grasping,maintaining and releasing the transferred piece of timber 11 beingtransferred, is synchronized with the movement of the load applicationrods 34, actuated by the translation actuators 35. Hence, the force isapplied on the transferred piece of timber 11, as sections of thetransferred piece of timber 11 are being maintained and supported by theset of grasping assemblies 22. The operation of the combination of eachset of grasping assemblies 22 and the corresponding load application rod34 will be explained in more details below.

In the embodiment shown, the translation actuator 35 is a pneumaticcylinder, but one skilled in the art will understand that, inalternative embodiments, the translation actuator can be any mechanismwhich drives the load application rod 34 longitudinally (i.e. any linearactuator), such as, without being limitative, a hydraulic cylinder, anelectric cylinder or the like. In an embodiment, the translationactuator 35 can be a servomotor.

One skilled in the art will also understand that, in other alternativeembodiments, the load application member 33 could differ from theplurality of load application rod and translation actuator assemblies ofthe embodiment shown and any other load application mechanism which canapply a momentary load on the piece of timber 11 can be used. Forexample and without being limitative, in an embodiment (not shown), theload application member 33 could rather include a clamping assembly,with the load application wheel 32 being connected to a rotatableactuation mechanism. The clamping assembly can be displaceable betweenthe inactive configuration (where no load is applied on the transferredtimber piece) and the active configuration (where a load is applied onthe transferred timber piece) by the action of the rotatable actuationmechanism connected to the load application wheel 32, such as to clamp asection of the transferred piece of timber 11 and apply or release theforce on the transferred piece of timber 11 by rotation, as sections ofthe transferred piece of timber 11 are being maintained and supported bythe set of grasping assemblies 22. In such an embodiment, the rotatableactuation mechanism can be any rotary actuator, such as an electricactuator connected to a secondary rotatable shaft different from theabove mentioned main rotatable shaft 21, onto which the load applicationwheel 32 is mounted and driving the secondary rotatable shaft inrotation. In an embodiment, the rotatable actuation mechanism can be aservomotor. One skilled in the art will understand that, in anembodiment, a plurality of clamping assemblies could also be provided,each one of the clamping assembly corresponding to a set of graspingassemblies 22.

In the embodiment shown, referring to FIGS. 4a and 4b , the deformationmeasuring system 38 of the stiffness measuring mechanism 30 determinesthe deformation of the transferred piece of timber 11 using a firstsurface position measuring assembly 40 and a second surface positionmeasuring assembly 42. The first surface position measuring assembly 40measures the position of a measure surface 11 b of the transferred pieceof timber 11 at a first measurement position, before the application ofthe force thereon by a corresponding one of the load application members33, and the second surface position measuring assembly 42 measures theposition of the measure surface 11 b of the transferred piece of timber11, at a second measurement position, with the force being applied onthe contact surface 11 a of the transferred piece of timber 11 by theload application member 33. One skilled in the art will understand thatthe first measurement position and the second measurement position areangular position of the transferred piece of timber 11, angularly spacedapart from one another, as the transferred piece of timber 11 is beingtransferred by the rotatable charging assembly 20.

In an embodiment, in order to allow the continuous and uninterruptedoperation of the rotary timber charger 10, i.e. continuous rotation, theload application member 33 applies the force on the transferred piece oftimber 11 and the deformation measuring system 38 measures the positionof the measure surface 11 b of the transferred piece of timber 11concurrently as the rotatable charging assembly 20 transfers it from thefirst carrier assembly 12 to the second carrier assembly 14. Hence, thestiffness measuring mechanism 30 does not interfere or negatively impacton the operation of the rotatable charging assembly 20, the mainrotatable shaft 21 of the rotatable charging assembly 20 rotatingcontinuously to transfer the corresponding piece of timber 11 from thefirst carrier assembly 12 to the second carrier assembly 14.

One skilled in the art will understand that in the course of the presentapplication, the expressions “without the force/load being applied onthe transferred piece of timber” before the force/load being applied onthe transferred piece of timber” or any corresponding expressions areunderstood to also include instances where a minimal load, for exampleand without being limitative, a load of less than about three pounds, isbeing applied on the transferred piece of timber 11.

One skilled in the art will understand that, in an embodiment, thedeformation measuring system 38 is configured to measure the position ofthe measure surface 11 b of the transferred piece of timber 11 of thetransferred piece of timber 11 at different points along the length ofthe transferred piece of timber 11, i.e. between each one of thetransfer wheels 24 of the rotatable charging assembly 20 where thetransferred piece of timber 11 is caused to deform by the momentaryapplication of a force by the load application member 33. Hence it willbe understood that, in an embodiment, each one of the first surfaceposition measuring assembly 40 and the second surface position measuringassembly 42 can include multiple sub-assemblies, each configured tomeasure the position of the measure surface 11 b of the transferredpiece of timber 11 at one of the different points along the length ofthe transferred piece of timber 11.

Once the position of the surface of the transferred piece of timber 11,with and without the force being applied to the transferred piece oftimber 11, has been gathered by the first surface position measuringassembly 40 and the second surface position measuring assembly 42, oneskilled in the art will understand that the deformation of thetransferred piece of timber 11 can easily be determined by calculations,for example and without being limitative, by a processor (not shown)coupled to the rotatable charging assembly 20, stiffness measuringmechanism 30 and deformation measuring system 38. One skilled in the artwill understand that from the calculated deformation of the transferredpiece of timber 11 and specific additional known data such as, withoutbeing limitative, the force applied by the load application member 33,the longitudinal position of the load application member 33 with regardsto the transferred piece of timber 11, the span between the graspingassemblies 22, the thickness of the transferred piece of timber 11, orthe like, the stiffness of the transferred piece of timber 11 can becalculated by the processor (for example by calculating the Young'smodulus of the transferred piece of timber 11). In an embodiment, thecalculated stiffness (and the correlated strength of the transferredpiece of timber 11) can subsequently be used to assign a stress grade tothe transferred piece of timber and thereby provide automated stressgrading of the pieces of timber 11 being transferred by the rotarytimber charger 10.

One skilled in the art will understand that, by determining thedeformation of the transferred piece of timber 11 through a comparisonof the measured position of the measure surface 11 b of the transferredpiece of timber 11, with and without the force being applied on thecontact surface 11 a of the transferred piece of timber 11 by the loadapplication member 33, over a range of angular positions of thetransferred piece of timber 11, the deformation is not influenced byimperfections which can be present at the measure surface 11 b of thetransferred piece of timber 11 (such as, without being limitative,tears, holes, slits or the like), or by a natural curvature of thetransferred piece of timber 11. Indeed, the determined deformation isthe actual deformation caused by the force being applied on the contactsurface 11 a of the transferred piece of timber 11 by the loadapplication member 33, in comparison to the position measured when noforce is being applied on the contact surface 11 a of the transferredpiece of timber 11.

In the embodiment shown, each one of the first surface positionmeasuring assembly 40 and the second surface position measuring assembly42 includes an optical measuring system (not shown) with a light source(not shown) and a light sensor (not shown), such as, without beinglimitative, a laser and a camera. Such optical systems are well known inthe art and need not be described in more details herein.

In an embodiment, the deformation measuring system 38 also includes arotary encoder 26 mounted close to the main rotatable shaft 21 and theload application wheel 32. The first surface position measuring assembly40 and the second surface position measuring assembly 42 are calibratedusing the rotary encoder 26, which is used to indicate the angularposition of the main rotatable shaft 21, and consequently, the positionof the corresponding one of the load application rod(s) 34 of the loadapplication wheel 32 which, in the embodiment shown, interacts with thetransferred piece of timber 11 to apply the momentary force on thecontact surface 11 a thereof.

One skilled in the art will understand that, in alternative embodiments,other systems configured to measure the position of a surface of thepiece of timber 11 can also be used. For example and without beinglimitative, in an embodiment where the actuator used for displacing acomponent interacting with the transferred piece of timber 11 to applythe force thereon (for example the load application rod(s) 34 or theload application wheel 32 and clamping assembly (not shown)) is aservomotor, or another mechanism using an encoder capable of determiningthe instant position thereof, the deformation measuring system 38 can beprovided by the encoder. Indeed, in such an embodiment, the encoderdetermines the position of the component interacting with thetransferred piece of timber 11 to apply the load thereon and thereby, byextension, the position of a surface of the transferred piece of timber11, initially (without the force being applied on the transferred pieceof timber 11) and upon application of the force on the transferred pieceof timber 11 (with the force being applied on the transferred piece oftimber 11). Hence, the encoder can measure the position of the surfaceof the piece of timber 11 at the first and second measurement positionsdescribed above.

Moreover, one skilled in the art will understand that, in an alternativeembodiment, the first surface position measuring assembly 40 and thesecond surface position measuring assembly 42 can be embodied in asingle assembly with a single optical system where the assembly can bemoved or rotated to measure the position of the measure surface 11 b ofthe corresponding transferred piece of timber 11 with and without theforce being applied on the contact surface 11 a of the transferred pieceof timber 11 by the load application member 33. In an alternativeembodiment, more than two measuring assemblies can also be used in orderto perform measuring of the deformation of the transferred piece oftimber 11 over a range of angular positions of the transferred piece oftimber 11, as is described in the present description.

In the embodiment shown, the stiffness of the transferred piece oftimber 11 is measured by a predetermined load being applied by the loadapplication rods 34 and the resulting deformation being measured andcalculated by the deformation measuring system 38. However, one skilledin the art will understand that, in an alternative embodiment, thestiffness of the transferred piece of timber 11 can alternatively bedetermined by reaching a predetermined deformation of the transferredpiece of timber 11 (as determined by the deformation measuring system38) and measuring the load applied by the corresponding load applicationmember 33, such as the load application rod 34 of the load applicationwheel 32, in the embodiment shown, in order to reach the predetermineddeformation.

Now referring to FIGS. 4a to 4f , an embodiment of a sequence ofoperation for the stress grading of the pieces of timber 11, duringtransfer thereof, will be described. In operation, the pieces of timber11 are successively conveyed transversally on the first carrier assembly12 towards the rotatable charging assembly 20. When one of thesuccessive pieces of timber 11 reaches the rotatable charging assembly20, in an embodiment (not shown), the piece of timber 11 is momentarilyheld against a stopper (not shown) until the rotatable charging assembly20 is ready to grasp the piece of timber 11.

When the rotatable charging assembly 20 is ready to grasp one of thesuccessive pieces of timber 11, the stopper is retracted and the pieceof timber 11 is grasped between the first grasping member 22 a and thesecond grasping member 22 b of the timber piece grasping assembly 22 ofthe rotating transfer wheels 24 (see FIG. 4a ).

The rotation of the transfer wheels 24 of the rotatable chargingassembly 20 subsequently rotates the transferred piece of timber 11.When the transferred piece of timber 11 has reached a first measurementposition, the first surface position measuring assembly 40 measures theposition of the measure surface 11 b of the transferred piece of timber11 (See FIG. 4b ). In the embodiment shown, the first measurementposition corresponds to the position of the piece of timber 11 beforethe application of the force thereon by a corresponding load applicationrod 34 of the load application wheel 32.

As the rotation of the transfer wheels 24 of the rotatable chargingassembly 20 and the consequent rotation of the transferred piece oftimber 11 continue, the load is applied to the contact surface 11 a ofthe transferred piece of timber 11 in order to cause a deformation ofthe transferred piece of timber 11. In the embodiment shown, the load isapplied onto the contact surface 11 a of the piece of timber 11 by theload application rod 34 of the load application wheel 32 angularlyaligned with the corresponding set of timber piece grasping assembly 22being brought in the active configuration through actuation of the loadapplication rod 34 by the translation actuator 35 (See FIGS. 4c and 4d). When the transferred piece of timber 11 has reached a secondmeasurement position, the second surface position measuring assembly 42measures the position of the measure surface 11 b of the transferredpiece of timber 11 (See FIG. 4d ). In the embodiment shown, the secondmeasurement position corresponds to the position of the transferredpiece of timber 11 where the deformation is maximal or reaches apredetermined deformation, following the application of the forcethereon by the corresponding load application rod 34 of the loadapplication wheel 32. In an embodiment, the deformation is maximal whenthe load application member 33 is in a maximal extension state.

Subsequently, the translation actuator 35 operatively connected to theload application rod 34 of the load application wheel 32, angularlyaligned with the corresponding set of timber piece grasping assembly 22engaging the transferred piece of timber 11, actuates the loadapplication rod 34 rearward to retract the load application rod 34towards the inactive configuration and therefore remove the forceapplied on the contact surface 11 a of the piece of timber 11, such thatthe piece of timber 11 returns to its original configuration (See FIG.4e ).

The piece of timber 11 is subsequently released from the timber piecegrasping assembly 22 of the transfer wheels 24 onto the second carrierassembly 14 and is conveyed transversally on the second carrier assembly14 away from the rotatable charging assembly 20 (see FIG. 4f ).

Once again, one skilled in the art will understand that, in analternative embodiment, the first measurement position can correspond tothe position of the transferred piece of timber 11 when the force isapplied on the contact surface 11 a by the corresponding loadapplication rod 34 of the load application wheel 32 and the secondmeasurement position thereby corresponds to the position of the piece oftimber 11 when the force is removed from the contact surface 11 a by thecorresponding load application rod 34 of the load application wheel 32.

Once again, one skilled in the art will understand that, in analternative embodiment, not shown, the load can be applied on thesurface of the transferred piece of timber 11 through a clampingassembly (not shown) initially engaging the piece of timber 11. In suchan embodiment, the clamping assembly would subsequently be displaced ina first direction to apply the force on the transferred piece of timber11 and cause a deformation of the piece of timber 11. When the forcewould be applied by the clamping assembly, in an embodiment, the pieceof timber would reach the second measurement position where the positionof the measure surface 11 b of the piece of timber 11 is measured. Theclamping assembly would subsequently be displaced in a second directionopposite the first direction to remove the force from the piece oftimber 11.

In an embodiment, the above described steps are coordinated by a controlsystem (not shown) based on the data of the rotary encoder 26 whichindicate that the transferred piece of timber 11 has reached one of theencoded positions. In other words, the control system operates such thatthe piece of timber 11 is grasped by the timber piece grasping assembly22 when the rotary encoder 26 indicates that the timber piece graspingassembly is positioned in the angular position to grasp the piece oftimber 11 from the first carrier assembly 12; the first surface positionmeasuring assembly 40 measures the position of the measure surface 11 bof the transferred piece of timber 11 when the rotary encoder 26indicates that the transferred piece of timber has reached a firstmeasured angular position; the translation actuator 35 actuates thecorresponding load application rod 34 forward when the rotary encoder 26indicates that the transferred piece of timber has reached a loadapplication angular position; the second surface position measuringassembly 42 measures the position of the measure surface 11 b of thetransferred piece of timber 11 when the rotary encoder 26 indicates thatthe transferred piece of timber has reached a second measured angularposition; the translation actuator 35 actuates the corresponding loadapplication rod 34 rearward when the rotary encoder 26 indicates thatthe transferred piece of timber has reached a load releasing angularposition; and the transferred piece of timber 11 is released by thetimber piece grasping assembly 22 when the rotary encoder 26 indicatesthat the timber piece grasping assembly is positioned in the angularposition to release the piece of timber 11 onto the second carrierassembly 14.

One skilled in the art will understand that, in an alternativeembodiment, other mechanism or method could be used to coordinate theoperation of the components in order to perform the above-describedsteps. In such an embodiment, the rotary encoder can save the angularposition of any of the specific components such as, the transfer wheels24, the load application wheel 32, the load application member 33 and/ora set of timber piece grasping assembly 22, or the like, when one of thesteps of the above mentioned method is performed.

One skilled in the art will understand that in an alternativeembodiment, the contact surface 11 a and the measure surface 11 b of thepiece of timber 11 could be inverted with respect to the embodimentshown. Moreover, even though in the embodiments shown, the contactsurface 11 a and the measure surface 11 b of the piece of timber 11 areopposed surfaces thereof, one skilled in the art will understand that,in an alternative embodiment, either one of the surfaces of the piece oftimber could be used as both the contact surface and the measuresurface.

Several alternative embodiments and examples have been described andillustrated herein. The embodiments of the invention described above areintended to be exemplary only. A person skilled in the art wouldappreciate the features of the individual embodiments, and the possiblecombinations and variations of the components. A person skilled in theart would further appreciate that any of the embodiments could beprovided in any combination with the other embodiments disclosed herein.It is understood that the invention can be embodied in other specificforms without departing from the central characteristics thereof. Thepresent examples and embodiments, therefore, are to be considered in allrespects as illustrative and not restrictive, and the invention is notto be limited to the details given herein. Accordingly, while specificembodiments have been illustrated and described, numerous modificationscome to mind without significantly departing from the scope of theinvention as defined in the appended claims.

1. A rotary timber charger comprising: a charging assembly with at leasttwo transfer wheels spaced apart from one another and mounted to a mainrotatable shaft, each one of the at least two transfer wheels having atleast one timber piece grasping assembly operative to grasp a section ofa piece of timber at a grasping position, release the section of thepiece of timber at a release position, and retain the section of thepiece of timber between the grasping position and the release position;and a stiffness measuring mechanism comprising: at least one loadapplication wheel positioned between consecutive transfer wheels, eachone of the at least one load application wheel comprising at least oneload application member configured to momentarily apply a load on thepiece of timber retained by a corresponding one of the at least onetimber piece grasping assembly of the consecutive ones of the at leasttwo transfer wheels; and a deformation measuring system comprising atleast one surface position measuring assembly measuring a first positionof a measure surface of the piece of timber and a second position of themeasure surface of the piece of timber, the second position of themeasure surface being angularly spaced-apart from the first position,with the load being applied by the at least one load application memberof the at least one load application wheel in at least one of the firstposition and the second position of the measure surface.
 2. The rotarytimber charger of claim 1, wherein the main rotatable shaft of thecharging assembly rotates continuously.
 3. The rotary timber charger ofclaim 1, wherein the first position of the measure surface is an angularposition thereof without the load being applied by the load applicationmember of the at least one load application wheel.
 4. The rotary timbercharger of claim 1, wherein the at least one load application wheel ismounted to the main rotatable shaft and rotates simultaneously with theat least two transfer wheels.
 5. The rotary timber charger of claim 4,wherein each one of the at least one load application member of the atleast one load application wheel includes a load application rod mountedto the load application wheel and a translation actuator operativelyconnected thereto to translate the load application rod between aninactive configuration wherein a timber piece abutting end of the loadapplication rod is spaced apart from a contact surface of the piece oftimber, opposed to the measured surface, and an active configurationwherein the timber piece abutting end of the load application rod abutsthe contact surface of the piece of timber.
 6. The rotary timber chargerof claim 5, wherein the at least one load application wheel comprises aplurality of load application members and wherein each one of the atleast two transfer wheels comprises a plurality of grasping assemblies,the amount of load application members corresponding to the amount ofgrasping assemblies and each one of the plurality of load applicationmembers being angularly aligned with a corresponding one of theplurality of grasping assemblies.
 7. The rotary timber charger of claim1, further comprising a rotary encoder indicating an angular position ofthe main rotatable shaft and wherein the at least one surface positionmeasuring assembly of the deformation measuring system is calibratedusing the rotary encoder.
 8. The rotary timber charger of claim 1,wherein the at least one surface position measuring assembly of thedeformation measuring system includes a first surface position measuringassembly configured to measure one of the position of the measuresurface of the piece of timber without the load being applied by theload application member of the at least one load application wheel andthe position of the measure surface of the piece of timber with the loadbeing applied by the load application member of the at least one loadapplication wheel and a second surface position measuring assemblyconfigured to measure the other one of the position of the measuresurface of the piece of timber without the load being applied by the atleast one load application member of the load application wheel and theposition of the measure surface of the piece of timber with the loadbeing applied by the load application member of the at least one loadapplication wheel.
 9. The rotary timber charger of claim 1, wherein eachone of the at least one timber piece grasping assembly comprises a firstand a second grasping members cooperating to engage opposite surfaces ofthe piece of timber and the load application member is mountedperipherally to a respective one of the at least one load applicationwheel and extends substantially tangentially thereto.
 10. A stiffnessmeasuring mechanism for a rotary timber charger having a rotatablecharging assembly including at least one set of timber piece graspingassemblies and being operative to transfer successive pieces of timberfrom a first carrier assembly to a second carrier assembly, thestiffness measuring mechanism comprising: at least one load applicationwheel positioned between consecutive grasping assemblies of the at leastone set of timber grasping assemblies of the rotatable chargingassembly, the at least one load application wheel comprising at leastone load application member configurable between an inactiveconfiguration where no load is applied on a transferred piece of timberand an active configuration where a load is applied on the transferredpiece of timber; and a deformation measuring system comprising at leastone surface position measuring assembly measuring a first position of ameasure surface of the transferred piece of timber and a second positionof the measure surface of the transferred piece of timber; wherein thestiffness measuring mechanism operates concurrently with the rotatablecharging assembly transferring the successive pieces of timber from thefirst carrier assembly to the second carrier assembly.
 11. The stiffnessmeasuring mechanism of claim 10, wherein the first position of themeasure surface of the transferred piece of timber corresponds to theinactive configuration of a corresponding one of the at least one loadapplication member and the second position of the measure surface of thetransferred piece of timber corresponds to the active configuration ofthe corresponding one of the at least one load application member. 12.The stiffness measuring mechanism of claim 10, wherein the chargingassembly of the rotary timber charger comprises a main shaft rotatableto engage in rotation the at least one set of timber piece graspingassemblies and the at least one load application wheel.
 13. Thestiffness measuring mechanism of claim 12, further comprising a rotaryencoder indicating an angular position of the main rotatable shaft andwherein the at least one surface position measuring assembly of thedeformation measuring system is calibrated using the rotary encoder. 14.The stiffness measuring mechanism of claim 10, wherein each one of theat least one load application member of the at least one loadapplication wheel includes a load application rod mounted to the loadapplication wheel and a translation actuator operatively connectedthereto to translate the load application rod between the inactiveconfiguration wherein a timber piece abutting end of the loadapplication rod is spaced apart from a contact surface of the piece oftimber, opposed to the measured surface, and the active configurationwherein the timber piece abutting end of the load application rod abutsthe contact surface of the piece of timber.
 15. The stiffness measuringmechanism of claim 14, wherein the at least one load application wheelcomprises a plurality of load application members and the rotatablecharging assembly comprises at least two transfer wheels, wherein eachone of the at least two transfer wheels comprises a plurality ofgrasping assemblies, the amount of load application memberscorresponding to the amount of grasping assemblies and each one of theplurality of load application members being angularly aligned with acorresponding one of the plurality of grasping assemblies.
 16. A methodfor measuring a stiffness of successive pieces of timber, for each oneof the successive pieces of timber, the method comprising the steps of:grasping the piece of timber at a grasping position; rotating the pieceof timber towards a release position; and releasing the piece of timber;concurrently with the step of rotating the piece of timber towards therelease position, the method further comprising: measuring a position ofa measure surface of the piece of timber at a first measurementposition; applying a load on the piece of timber; measuring a positionof the measure surface of the piece of timber at a second measurementposition as the load is applied on the piece of timber; and removing theload from the piece of timber.
 17. The method of claim 16, wherein thestep of rotating the piece of timber towards the release position isperformed by a continuous rotation of the piece of timber.
 18. Themethod of claim 16, wherein the first measurement position is theposition of the measure surface of the piece of timber without the loadbeing applied on the piece of timber.
 19. The method of claim 16,wherein the step of grasping the piece of timber at a grasping positionand continuously rotating the piece of timber towards a release positioncomprise temporarily engaging opposite surfaces of the piece of timberat grasping positions along a length of the piece of timber.
 20. Themethod of claim 19, wherein the step of applying a load on the piece oftimber comprises engaging the piece of timber using at least one loadapplication member, along at least one section of the piece of timberlocated between the grasping positions.